HALOANAEROBIUM CONGOLENSE SP-NOV, AN ANAEROBIC, MODERATELY HALOPHILIC, THIOSULFATE-REDUCING AND SULFUR-REDUCING BACTERIUM FROM AN AFRICAN OIL-FIELD

A strictly anaerobic, moderately halophilic, Gram-negative, non-motile rod-shaped bacterium was isolated from an oil-well head sample of an offshore Congolese oil field. The strain, designated SEER 4224(T) (T t ype strain), grew optimally at 42 degrees C and pH 7.0 in a complex me dium containing 10% NaCl with a generation time of 2.5 h. Strain SEER 4224(T) grew on a range of carbohydrates including fructose, galactose , D-glucose, maltose, D-mannose, D-ribose, sucrose, and trehalose. Yea st extract and/or bio-Trypcase was required for growth on carbohydrate s and could not be replaced with amino acids and/or vitamins. The end- products from glucose fermentation were acetate, H-2, and CO2. Thiosul fate and elemental sulfur were used as electron accepters. Thiosulfate improved carbohydrate utilization and biomass yields. The G+C content of the isolate was 34 mol%. Ribosomal 16S rRNA sequence analysis show ed that strain SEER 4224(T) is a new member of the genus Haloanaerobiu m. The lack of DNA homology with H. acetoethylicum, its closest relati ve, as determined by DNA-DNA hybridization supports the designation of strain SEER 4224(T) as a new species, Haloanaerobium congolense sp. n ov. The type strain is SEER 4224 (= DSM 11287).